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| <div class="section" id="count-if"> |
| <h1><a class="toc-backref" href="./querying-algorithms.html#id1479">count_if</a></h1> |
| <div class="section" id="id567"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename Sequence |
| , typename Pred |
| > |
| struct <a href="./count-if.html" class="identifier">count_if</a> |
| { |
| typedef <em>unspecified</em> type; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id568"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Returns the number of elements in <tt class="literal"><span class="pre">Sequence</span></tt> that satisfy the predicate <tt class="literal"><span class="pre">Pred</span></tt>.</p> |
| </div> |
| <div class="section" id="id569"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/count_if.hpp" class="header">boost/mpl/count_if.hpp</a>> |
| </pre> |
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| <div class="section" id="id570"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
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| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
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| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> |
| <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> |
| <td>A sequence to be examined.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">Pred</span></tt></td> |
| <td>Unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> |
| <td>A count condition.</td> |
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| <div class="section" id="id571"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt> and unary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a> <tt class="literal"><span class="pre">pred</span></tt>:</p> |
| <pre class="literal-block"> |
| typedef <a href="./count-if.html" class="identifier">count_if</a><s,pred>::type n; |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
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| <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> |
| <pre class="last literal-block"> |
| typedef <a href="./lambda.html" class="identifier">lambda</a><pred>::type p; |
| typedef <a href="./fold.html" class="identifier">fold</a>< |
| s |
| , <a href="./long.html" class="identifier">long_</a><0> |
| , <a href="./if.html" class="identifier">if_</a>< <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">1</span></tt><p,<a href="./placeholders.html" class="identifier">_2</a>>, <a href="./next.html" class="identifier">next</a><<a href="./placeholders.html" class="identifier">_1</a>>, <a href="./placeholders.html" class="identifier">_1</a> > |
| >::type n; |
| </pre> |
| </td> |
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| </table> |
| </div> |
| <div class="section" id="id572"> |
| <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> |
| <p>Linear. Exactly <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a><s>::value</span></tt> applications of <tt class="literal"><span class="pre">pred</span></tt>.</p> |
| </div> |
| <div class="section" id="id573"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| typedef <a href="./vector.html" class="identifier">vector</a><int,char,long,short,char,long,double,long> types; |
| |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_float<_> >::value), ==, 1 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_same<_,char> >::value), ==, 2 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./count-if.html" class="identifier">count_if</a>< types, is_same<_,void> >::value), ==, 0 ); |
| </pre> |
| </div> |
| <div class="section" id="id574"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <p><a class="reference internal" href="./querying-algorithms.html">Querying Algorithms</a>, <a class="reference internal" href="./count.html">count</a>, <a class="reference internal" href="./find.html">find</a>, <a class="reference internal" href="./find-if.html">find_if</a>, <a class="reference internal" href="./contains.html">contains</a></p> |
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